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Wyszukujesz frazę "Koeshidayatullah, A." wg kryterium: Autor


Wyświetlanie 1-2 z 2
Tytuł:
Unraveling cementation environment and patterns of Holocene beachrocks in the Arabian Gulf and the Gulf of Aqaba : stable isotope approach
Autorzy:
Koeshidayatullah, A.
Al-Ramadan, K.
Powiązania:
https://bibliotekanauki.pl/articles/2059746.pdf
Data publikacji:
2014
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
cementation
beachrocks
stable isotope
Arabian Gulf
Gulf of Aqaba
Opis:
This paper analyses Holocene beachrocks from the Arabian Gulf and the Gulf of Aqaba to explain the mechanisms that influence the cementation process in these areas. Holocene beachrocks in the Gulf of Aqaba are composed of predominantly terrigenous material derived from erosion of adjacent uplifted Precambrian basement, while the beachrocks in the Arabian Gulf are composed mainly of marine bioclasts and wind-blown siliciclastic sands. The cements of beachrocks in both areas show three textural varieties: (1) isopachous phreatic acicular aragonite; (2) a micritic envelope of high-Mg calcite (HMC); (3) meniscus and gravitational vadose HMC. Radiocarbon dating of beachrock samples from the Arabian Gulf yielded ages from ca. 2300 to 660 yr cal BP whereas samples from the Gulf of Aqaba range in age between 5500 and 2800 yr cal BP. Oxygen isotope values range from 2.6 to 4.4‰ respectively for the Arabian Gulf whereas the Gulf of Aqaba values range from 1.2 to 1.5‰. Carbon isotope values range from 3.2 to 5.9‰ for the Arabian Gulf whereas those from the Gulf of Aqaba range from 3.8 to 4.6‰. The values of δ18OVPDB and δ13CVPDB in the beachrocks of both areas suggest a marine origin. The beachrocks of the Arabian Gulf were precipitated under high evaporation conditions, while beachrocks from the Gulf of Aqaba were precipitated in normal shallow-marine conditions. The mineralogy and textural habits suggest that cementation of these beachrocks started within the shallow-marine phreatic zone.
Źródło:
Geological Quarterly; 2014, 58, 2; 207--216
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Formation conditions and diagenetic evolution of Sand Roses in clastic sabkhas along the Arabian Gulf Coastal Region, Eastern Saudi Arabia
Autorzy:
Al-Hussaini, A.
Koeshidayatullah, A.
Al-Ramadan, K.
Powiązania:
https://bibliotekanauki.pl/articles/2059800.pdf
Data publikacji:
2015
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
sand roses
desert
diagenesis
gypsum
Arabian Gulf
Opis:
This field, petrographic and geochemical study aims at constraining the formation and diagenetic evolution of sand roses (desert roses) in interdune sabkhas in Eastern Saudi Arabia. These “roses”, which are mainly cemented by gypsum, carbonate, and clay minerals, occur as disc-shaped and spherical flower-like crystals. Sands, within the sand roses, are moderately-sorted, medium-grained, and sub-arkosic. Gypsum typically exceeds 20% of the volume of the roses, and locally gypsum is partly transformed to anhydrite. In addition to gypsum and anhydrite, early diagenetic modifications include precipitation of grain coating clay, dissolution of unstable grains (e.g., feldspar grains), and weak mechanical compaction. Iron oxide cement was formed when the sand roses exposed to the surface. The XRD and petrographic data indicate an increase in amounts of gypsum cement from the water table upward towards the sabkha surface. The sand roses also are larger and lighter in colour away from the water table. This study is expected to provide a better understanding of the mode of sand roses formation in the interdunes areas, as well as the diagenetic alterations in both phreatic and vadose zones.
Źródło:
Geological Quarterly; 2015, 59, 1; 71--78
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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